Microelectromechanical systems, or MEMS-based devices, can be used in a variety of applications, such as accelerometers, gyroscopes, pressure sensors or transducers, displays, optical switches, and fluid ejectors. Typically, one or more individual devices are formed on a single die, such as a die formed of an insulating material, a semiconducting material or a combination of materials. The die can be processed using semiconducting processing techniques, such as photholithography, deposition, and etching.
A fluid ejection device can have multiple MEMS devices that are each capable of ejecting fluid droplets from a nozzle onto a medium. In some devices that use a mechanically based actuator to eject the fluid droplets, the nozzles are each fluidically connected to a fluid path that includes a fluid pumping chamber. The fluid pumping chamber is actuated by the actuator, which temporarily modifies the volume of the pumping chamber and causes ejection of a fluid droplet. The medium can be moved relative to the die. The ejection of a fluid droplet from a particular nozzle is timed with the movement of the medium to place a fluid droplet at a desired location on the medium.
The density of nozzles in the fluid ejection module has increased as fabrication methods improve. For example, MEMS-based devices fabricated on silicon wafers are formed in dies with a smaller footprint and with a nozzle density higher than in previous dies. One obstacle in constructing smaller dies is that the smaller footprint of such devices can reduce the area available for electrical contacts on the die.